The Knights of the Ebon Blade (mirroring the Knights of the Silver Hand) are an organization of renegade death knights. Their base is at Acherus: The Ebon Hold in the Eastern Plaguelands. Its primary function is to guide new renegade death knights.
Freed from the grasp of the Lich King, his former death knights have regrouped against him under the banner of Highlord Darion Mograine.

Creation

The Knights of the Ebon Blade were originally an army of Scourge death knights trained in the halls of Acherus. They were created (or so they were told) for the purposes of destroying both the Scarlet Crusade in their enclave east of Tyr's Hand, and the Argent Dawn at Light's Hope Chapel. In truth, the entire plan was conceived by the Lich King himself not to destroy the Argent Dawn, but rather to use the death knight legion as bait to lure out the Highlord of the resurgent Order of the Silver Hand, Tirion Fordring.
During the Battle for Light's Hope Chapel, where ten thousand Scourge faced off against three hundred defenders of the Light, the corrupted Ashbringer wielded by the death knight commander, Highlord Darion Mograine, refuses to obey its wielder. When Fordring arrives, his powers of the Light prove too great for even ten thousand to oppose, and Mograine orders his death knights to surrender. Fordring scolds Mograine for his foolishness and tells him that Arthas sent him and his death knights on a suicide mission. As they await the paladin's judgment, they witness a vision of Mograine's father, Alexandros, the legendary Ashbringer himself. He told his son that he would one day wield the Ashbringer and use it to mete out justice, but "that day is not today".

The Lich King himself arrives not long afterwards and confirms that he had indeed sent the death knights to their deaths in order to bring Fordring out of hiding. Enraged by this treachery, Mograine attacks, but the Lich King swats him aside in one hit and focuses his attention on Fordring, incapacitating him with a crippling spell and knocking back the Argent soldiers who charged in. Remembering the words spoken by his father, Mograine throws the corrupted Ashbringer to Fordring, whose powers of the Light succeed in purifying it. With the purified blade in hand, Fordring charges into the Lich King and throws him back. Leaving their battle for another day, the lord of the Scourge flees back to Northrend, warning Tirion that: "When next we meet, it won't be on holy ground, paladin."

After Arthas' departure, Fordring calls for the union of the Argent Dawn and the Order of the Silver Hand into the Argent Crusade, intended to bring the war to Icecrown itself. Mograine pledges himself and his knights to the same cause, naming his new order the Knights of the Ebon Blade. With their free will restored, Mograine and his death knights return to Acherus and capture it, destroying the Scourge remnants within. With their new base secured, Mograine then sends his knights to rejoin their people, sending them to throw themselves at the mercy of either King Varian Wrynn in Stormwind (if their race belonged to the Alliance) or Warchief Garrosh Hellscream in Orgrimmar (if they belonged to the Horde).

Reputation

All players, with the exception of death knights, start out at neutral with the Knights of the Ebon Blade. (Upon the completion of [55] The Light of Dawn, death knights are raised to friendly reputation.)
Reputation with Knights of the Ebon Blade can be earned by completing the following daily quests.

Additionally, as with some other factions, reputation can be gained through Championing via the [Tabard of the Ebon Blade], or by trading 1 [Emblems of Triumph] for 1 [Ebon Blade Commendation Badge] at the Emblem of Triumph Quartermaster in Dalaran.